Configuring Cyta SIP Trunk with 3CX

Cyta Logo

Step 1: Choosing SIP trunk type

Cyta has 2 ways of providing customers the SIP Trunk:

  • Over the Internet (requires a Static Public IP Address) - For users that may have their 3CX system installed anywhere in the world or hosted in the Cloud.
  • Over the Cyta copper/fiber network - Can only be used when your 3CX system is in a physical location where the Cyta copper/network exists.

Step 2: Adding Cyta SIP Trunk ‘Over the Internet’

Collecting 3CX Configuration Settings

Once your “Over the Internet” SIP Trunk has been activated by Cyta, you will receive the SIP Trunk information via email.

Make sure you have:

  • Registration/Authentication Number
  • Telephone Number you have been allocated
  • Outbound Proxy server
  • Username for Authentication
  • Password

Adding the Trunk

  1. General instructions outlining how to add a new SIP Trunk to your 3CX installation can be found here.
  2. Enter the main trunk number in the national format (e.g. 22251245).
  3. Add the trunk to the PBX via the Management Console. Under the “General” tab enter the following information:
  1. “Outbound Proxy server” in the “Outbound  Proxy” field.
  2. “Registration/Authentication Number” in the “Authentication ID (aka SIP User ID)”  field.
  3. “Username for Authentication” in the “3 Way Authentication Password” field.
  4. “Password” in the “Authentication Password” field.
  1. Under the “Options” tab, check the option “Put Public IP in SIP VIA Header” and enter the Static Public IP of your 3CX system.

Cyta SIP Trunk Provider - Public IP

  1. After doing this, scroll to the top of the page and press OK to create the SIP Trunk in 3CX.

Step 3: Adding Cyta SIP Trunk ‘Over the Cyta Network’

Network Topology

To use an “Over the Cyta Network” Cyta SIP Trunk with 3CX, the 3CX Server needs to have a second network card. It will only be used for traffic from and to the Cyta servers. The network topology should look similar to the following:

Cyta SIP Trunk Provider - Network Topology

NIC 1 should connect to the main LAN through which the 3CX Server will have access to the internet and will also be the LAN on which Extensions are connected to. The Cyta router can also be used for internet access. In that case you will connect both NICs on the same CYTA router.

NIC 2 will only cater for traffic from/to the Cyta servers and must be connected to the Cyta router and the port that they have specified (usually port 4).

3CX Server NIC Setup

  • NIC 1: Apply the necessary network settings required by your network.
  • NIC 2: You must manually configure the Cyta WAN IP address that has be given to you and as per the instruction by Cyta, e.g.:


Important! NIC 2 must not have a Default Gateway configured and the DNS servers must be blank.

Adding Static Routes

Add a static route so that the traffic from the 3CX server towards the Cyta servers is routed out through the correct Gateway. The Gateway you should use is given to you by Cyta.

Windows OS: Open a command prompt using the Run as Administrator option, then run the following commands:

route -p add 10.224.150.7 MASK 255.255.255.255 [Gateway IP given by Provider] metric 1

Note: You need to do this for all Cyta IPs. Your Cyta representative can give you the list of IPs to add.

Debian: The most common way of configuring Static Routes is by adding them to /etc/network/interfaces. Use the same IPs and Netmasks as above and don’t forget to add them for both post-up and pre-down.

Example: up ip route add [Registrar IP] via [Gateway IP] dev [NIC ID] src [NIC IP]

Determine the Outbound Proxy

Once static routes are added, find the IP address of the Outbound Proxy you must use. On Windows OS you can use the “nslookup” command from the Command Prompt:

Cyta SIP Trunk Provider - Outbound Proxy

Make note of the IP of the Outbound Proxy as you will need it in the next step.

Adding the trunk:

  • In the "Options" tab, choose "Use this IP Address."
  • Click on "Select which IP to use in 'Contact' (SIP) and 'Connection'(SDP) fields."
  • Enter the IP address you configured on NIC 2. This should be provided to you by Cyta in the form of “PBX WAN IP Address”.
  • For the "Outbound Proxy," you should use the IP address obtained in the previous step.

Hosted by 3CX support

Cyta trunks are supported for Hosting by 3CX but you can only add them using the “Over the Internet (requires a Static Public IP Address)” method so make sure you order the right product if you choose to host your PBX with 3CX.

About Cyta

Cyta is the leading brand in the Cyprus telecommunications sector, providing integrated electronic communication solutions. By spearheading the technological development and convergence of telecommunications and IT, Cyta is now the pioneer of communications and multimedia advancement in Cyprus, offering a broad range of innovative services and ICT solutions to both the consumer as well as the business market. Cyta’s Business Telephony SIP trunking service is a cost-effective and flexible solution which offers free interoffice calls, easy scalability and business continuity, and is now available for 3CX customers to use with their PBX.

Last Updated

This document was last updated on 7 July 2023

https://www.3cx.com/docs/sip-trunk/cyta-cyprus/